The invention relates to a rope brake for an elevator installation for braking a rope coupled to a car, with a stop that is immovable in the longitudinal direction of the rope and at least one brake shoe, it being possible for the rope to be led through between the stop and the brake shoe, and it being possible for the brake shoe to be moved back and forth between a braking position, pressing the rope against the stop, and a release position, releasing the rope, and with a linear drive coupled to the brake shoe for releasing the rope, the at least one brake shoe being able to be transferred by means of the linear drive into its release position against the action of a braking force acting on it in the braking position.
Rope brakes are known, for example, from EP 0 708 051 A1. They can be used for example for reliably braking a rope that is coupled to a counterweight of the elevator installation and is held on the car that can be made to travel up and down along a traveling path, in that the at least one movably disposed brake shoe assumes its braking position and the rope is thereby pressed against the stop. To transfer the brake shoe into its release position, an electric motor is used in the case of the rope brake that is known from EP 0 708 051 A1, which motor is coupled by means of a chain linkage and a magnetic coupling to a shaft, fixed to one end of which is a spiral spring that is fixedly held at the other end and is in operative connection by means of a thread with a piston that is held such that it is displaceable and rotationally fixed and on which the movable brake shoe is held. The electric motor provides a rotary drive which sets the shaft in rotation, so that the spiral spring is tensioned and at the same time the brake shoe is transferred into its release position. If the rope is to be braked, the magnetic coupling is released and, as a result, the operative connection between the rotary drive and the shaft is interrupted. This then has the consequence that the spiral spring is relaxed, the shaft being set in rotation and, as a result, the brake shoe moved in the direction of the stop, so that the rope is pressed against the stop. The actual braking force is produced by a spring force which acts on the stop that is immovable in the longitudinal direction of the rope but movable in the transverse direction of the rope. For the movable brake shoe, this requires an additional distance which must be covered, since the stop that is displaceable in the transverse direction of the rope can give way until the braking force is built up.
The rope brake known from EP 0 708 051 A1 has a complex construction with a large number of components. This makes the rope brake susceptible to faults. Furthermore, the braking process that can be achieved by means of the rope brake is relatively slow, since a not inconsiderable time is required to allow the rope to be effectively braked by means of the rotation in the thread after the rope brake is activated.
U.S. Pat. No. 5,228,540 discloses a rope brake in which the brake shoe can be transferred into its braking position by means of a pivoting lever. For this purpose, two compression springs and a hydraulic piston-cylinder assembly are articulated on the free end of the pivoting lever. The compression springs permanently exert on the pivoting lever a spring force which attempts to pivot the pivoting lever in such a way that the brake shoe assumes its braking position. Counter to the action of the compression springs, the pivoting lever may be held by means of the piston-cylinder assembly in a position in which the brake shoe releases the rope. If the brake shoe is to assume its braking position, for this purpose the pivoting lever must be pivoted and at the same time the piston of the piston-cylinder assembly moved counter to the pressure medium acting on it. This has the consequence that the braking force provided by the compression springs is only partly available to the brake shoe for braking the rope, since part of the braking force must be used for moving the piston. Furthermore, the braking process that can be achieved is relatively slow, since some time is required to allow the rope to be effectively braked by means of the pivoting movement of the pivoting lever after the rope brake is activated.
It is an object of the present invention to develop a rope brake of the type mentioned at the beginning in such a way that it has a simpler construction and with it the rope can be braked within a shorter time.